Pneumatic tool



- Nv. 27, 192s. l 1,692,889

A. T. DUPONT PNEUMATIC TooL Filed Nov. 8., 1927 Patented Novr 27, 1928.

UNITE@ STATES ANDREW T. DUPONT, 0F WASHINGTON, DISTRICT OF COLUMBIA.

PNEUMATIC TOOL.

Application filed. November 8, 1327. Serial No. 231,954.

My invention relates to elastic fluid engines, and particularly to power operated percussive tools such as rock drills, mining machines, pneumatic hammers and the like the operation of which is effected by elastic motive fiuid under pressure alternately admitted into a working cylinder on opposite sides of a. reciprocating piston freely mounted therein.

One object of my invention is to improve the operation of devices of the aforesaid character.

Another object of my invention is to increase the reciprocations of the percussive element.

A further object is to augment the force of the blow struck by the percussive element.

Still another object of my invention is to provide suction creating means during the working stroke of the percussive element so that the effective pressure may be higher than in the ordinary type of tool.

With these and other objects in view, my invention consists in the features of construction and operation set forth in the following specification. i

Referring` grammatic equipped with to the drawings: Fig. 1 is a diashowing i of a pneumatic tool my invention. Fig. 2 is a view similar to Fig. 1 but showing the piston and valve in a different position. j

In the drawings is shown a tool having a cylinder comprising' a smaller rearward bore 1 and a larger the cylinder is a piston P having an enlarged head 3 fitting the forward bore and a shank l sliding in the rearward bore. The head and shank are connected by a reduced portion or neck 5.

The rear end of the bore 1 is in constant communication with the main pressure supply 6. A. passage 7 connects the supply 6 with the forward end of the bore 1 near its point of juncture with the larger bore 2, in such manner that when the piston is at the end of its rearward stroke, pressure fluid is admitted against the forwardly acting surfaces A. and A of the piston P.

Disposed longitudinal of the cylinder is a valve chest 8 in which a three-spool valve V is slidably mounted. A passage 9 leads from the fluid inlet 6 to the rearward end of the valvechest into which it opens through two ports 10 and 11. Another passage 12 leads from the forward end of the larger bore 2 to the valve chest 8, this passage 12 opening thereinto through two ports 13 and 14C, port 14 forward bore 2, Sliding in being situated diametrically across from port 11.

An ejector device E is conventionally shown and is composed of a live orifice 15 and an exhaust orifice 16. I designate 15 as a live orifice because it is adapted to be connected, at times, with the main fluid supply 6, while l term 16 an exhaust orific for the reason that it is designed to be used as an exhaust passage for the forward end of the larger bore 2.

A passage 17 leads from the live ejector -or'if lice to the valve chest 8 having a. port 18 opening thereinto diametrically opposite port 10, while another passage 19 connects the exhaust ejector orifice 16 with the valve chest, having a port opening in the said chest as shown at 20, directly opposite port 13.

A. passage 21 leads from the bore 1 to the rear end of the valve chest, from which end of the chest there is a leak port 22 connected permanently with the atmosphere. From the forward end of the valve chest there is a passage 23 which leads to the rear end of the bore 2. Passages 21 and 23 are controlled by the piston and are the so called kicking passages. A suitable valve 27 is placed on the leak port 22 so as to control the exhaust area. for the fluid esca-ping from the rear end of the valve chest. This is a well known and old feature in the pneumatic tool art as is exemplified in the U. S. Patent 955,686 of 1910 and needs no further description.

A main exhaust port for the cylinder bore 2 is shown at 24, this port being` adapted to be controlled by the enlarged head 8 of the piston. An auxiliary exhaust passage 25 leads from the bore 2 at such point that it will Abe covered by the rearward edge of the piston head 8 during the rear stroke of the latter some time after the head 3 has covered the main exhaust port 24. This passage 25 leads to the valve chest diametrically across a passage 26 connected with passage 19.

At T is indicated a tool or chuck extending into the cylinder and adapted to be struck by the hammer or piston P.

In operation, supposing the parts to be in the position shown in'Fig. 1, fluid is being admitted to the rear ends of bores 1 and 2 while the front end of bore 2 is open to exhaust through port 24;' and also through passage 12, port 13, across the valve chest, port 20, passage 19 and exhaust orifice 16 of the ejector. At the same time live pressure fluid is being supplied to the live orifice 15 through passage 9, port 10, across the valve chest, port tion of the exhaust fluid contained in the forward end of the bore 2 due to the suction caused at 1G by the live air issuing from 15.

The valve V is being held at the end of its leftward travel by the live fluid supplied through passages 6, 7, across the neck portion 5 of the piston, into the rear end of bore 2 and passage 23, it being noted that at this time the-left end face of the valve is vented to atmosphere through leak port 22.

The pressure acting on the areas A and A of the piston drives the latter' forward, and this action is concomitant with that of the suction in front of the area B of the head 8. When the enlarged head of the piston covers exhaust port 24 compression would set in the forward bore 2 were it not for the provision of the continued exhaust through the exhaust orifice 1G of the ejector which insures an unimpeded blow of the hammer upon the tool.

Cut off of the pressure fluid acting against area A occurs at about the time when the forward edge of the enlarged piston head reaches the forward edge of exhaust port 24. From this time until the rear edge of the enlarged piston head uncovers the rearward edge of exhaust port 24, the pressure fluid acts expansively in the rear chamber 2 while full line pressure is maintained against area A of the piston shank. During this period the pressure in front of piston head 3 in the forward chamber 2 is being rarefied through the action of the ejector E the net resultbeing an increase of the driving pressure over line pressure due to the vacuum produced in front of the piston. The impulse of the piston is therefore augmented and a full, quick and sharp blow is delivered to the chuck or tool T.

As soon as the rear edge of the piston head 3 has uncovered exhaust port 24, the pressure fluid acting against the forward face of the valve drops and the valve having atmospheric pressure on each of its end faces, is in balanced condition. W hen the piston shank uncovers passage 21, live fluid is again admitted to the rearward face of the valve and the latter shifts to its forward position.

We now have the valve and piston in the yposition shown in Fig. 2.

In this position live fluid admission to the ejector is cut on", ports 10 and 18 being closed by the valve. Pressure fluid is admitted through passages 6, 9, port 11, across the valve chest, port 14 and passage 12, in the forward end of the enlarged cylinder bore to act against the surface B of the piston head 3.

.The rear end of the bore 2 is open to exhaust through port 24 and also through passage 25, across the valve chest, to passages 26, 19 and out thro-ugh the exhaust orifice 16 of the ej ector E. Exhaust port 24 becomes covered by the piston head 24. Meanwhile the shank 4 has covered the port opening of passage 21 and the pressure acting against the rearward valve face is exhausting through port 22. After the head 3 has covered the port opening of the auxiliary exhaust passage 25 compression sets in passage 23 and acts against the forward valve face and together with the live air admitted thru passage 7 overcomes the pressure holding the valve tothe right. The parts are then returned to the position shown in Fig. 1 ready for another cycle of operations.

VVhilel have shown my invention applied to a tool of the so-called semi-valveless type, it is to be understood that it may be embodied 1n other types as well and that l do not limit myself to such specific construction but intend the scope of my invention as disclosed herein and defined in t-he appended claims to include modifications and other adaptations which this disclosure will readily suggest to persons skilled in the art.

Having thus described my invention, what 1 claim as new, and desire to secure by Letters Patent, is:

1. 1n a fluid operated percussive tool, a

cylinder having differential chambers, a piston having an enlarged head fitting in the larger of said chambers and a shank fit ting in the smaller of said chambers, an ejector, means for connecting the ejectorto the source of pressure fluid and to one sid-e of the larger cylinder chamber, ports and passages for admitting pressure fluid to t-he cylinder chambers to operate the. piston, a

valve controlling certain of said4 ports and passages and the connection betweenY the i source and the ejector and between the ejector and the larger cylinder chamber and means controlled by the piston shank for reversing the valveat the end of each piston stroke.

2. In -a fluid operated percussive tool, in combination, a differential cylinder, a vdifferential piston therein, a valve and an ejector, means uncontrolled by the valve for admitting pressure fluid in the cylinder to drive the piston forwardly, means controlled by the valve for admitting pressure fluid in the cylinder to drive the piston rearwardly, means controlled by said valve for simultaneously connecting the ejector to the source of pressure and to one end of the cylinder, and means'controlled by the smaller piston portion for controlling said valve.

3. ln a pneumatic tool, a cylinder composed of two chambers of different sizes, a piston having a head fitting the larger chamber and a shank fitting the smaller chamber, means for constantly admitting pressure fluid against the piston shank, means controllcd by said shank for admitting pressure uid against one side of the enlarged piston head, a valve, means'controlled by said valve for admitting pressure luid on the opposite side of the piston head, a main exhaust port in the larger cylinder chamber controlled by said piston head, an auxiliary exhaust port at each end of the main cylinder chamber, an ejector, and means controlled by said valve for connecting the ejector to the source of pressure and to one of said auxiliary exhaust ports.

l. In a pneumatic tool, in combination, a differential cylinder a piston therein having` two forwardly acting pressure areas and a single rearwardly acting pressure area, a valve.j an ejector comprising a live air ori- (ice and an eiha ust orifice, means for simultaneously connecting` the live air orilice and tie two forwardly acting,v pressure areas to the source of pressure fluid while the rearwardly acting pressure area is connected to the exhaust orilice, means controlled by said piston for discontinuing the connection between the source and one of said forwardly acting pressure areas when the piston has accomplished a portion only of its forward stroke and means controlled by said valve for discontinuing the connection between the source and the live air orifice and that between the rearwardly acting pressure area and the exhaust orifice upon comple-tion of the piston stroke.

ln testimony whereof I hereunto affix my signature this 8th day ol November, 1927.

ANDREV T. DUPONT. 

